gnu: emacs-picpocket: Update to 40.

Fix version string as well:
<https://lists.gnu.org/archive/html/guix-devel/2018-11/msg00286.html>.

* gnu/packages/emacs.scm (emacs-picpocket): Update to 40.

gnu/packages/emacs.scm

@@ -11735,8 +11735,8 @@ file.")
       (license license:gpl3+))))
 
 (define-public emacs-picpocket
-  (let ((version "20180610.1059") ; taken from melpa
-        (commit "ce4b6ed088384f2414af82e8e4eae5b92c2874bf"))
+  (let ((version "40")
+        (commit "6fd88b8711c4370662c0f9c462170187d092a046"))
     (package
       (name "emacs-picpocket")
       (version version)
@@ -11748,7 +11748,7 @@ file.")
                (commit commit)))
          (file-name (git-file-name name version))
          (sha256
-          (base32 "15vpbcv83mc4j1pvrk7xic0klh2bl9gzg2xxs7c2lmnix52hy8mv"))))
+          (base32 "1mdzzxf7xm7zwrpnqqxa27d1cr31pd72d7ilbwljv13qp177a3yw"))))
       (build-system emacs-build-system)
       (arguments ; needed for running tests
        `(#:tests? #t